Relative links let you use different host names, ports, and protocols (https/http) for the same server. This is helpful when using a load balancer and wanting to see the individual servers behind it. For example, maybe the SSL connection is terminated at the load balancer and you want to name your servers behind the load balancer for easier troubleshooting. Being able to use different host/port/protocols is also helpful in development because you can use different parameters than the production site. Absolute links that are internal to the forum are fine if they respect the hostname, port, and protocol.
Iβm not sure if you think absolute links are better, but if you do, then there are a lot more links with the opposite problem.